The combination of fruit and dry breakfast cereals has significant consumer appeal. The food industry, recognizing the wide enjoyment of fresh fruit with dry breakfast cereal has in the past developed products composed of dry cereal combined with dehydrated fruits. Although enjoying some consumer acceptance, manufacturers of breakfast cereals have been aware of the deficiencies inherent in breakfast products in which a dry cereal is packaged with a dehydrated fruit and have sought methods to improve upon the quality of these products.
Dried fruits such as raisins, dried apples, dried peaches, i.e., fruits containing moisture between 13 to 23%, tend to dehydrate further and become hard and chewy when added to breakfast cereals that contain moisture at levels of between 2 and 3%. This is generally noticable after about four to eight weeks of storage, especially when the fruit's moisture drops below 10% which is the critical moisture for most dry fruits. At this point the fruit becomes unacceptably hard. This generally causes the cereal base to increase in moisture to above 5% beyond which level the cereal begins to lose its crispness.
To retard moisture migration from the fruit to the cereal base it has been the practice over the years to add some moisture to the cereal base, usually amounts sufficient to raise the moisture of the cereal to about 7.5%. This allows the fruit, i.e., raisins, to remain soft even after equilibration. However, the moisture level of the cereal flakes becomes dangerously close to the critical point where the flake begins to lose its crispness (around 7-8%).
Attempts to solve this problem are disclosed in U.S. Pat. No. 4,256,772 by Shanbhag et al. wherein the fruit to be blended with the cereal is infused with an aqueous solution of polyhydric alcohol and a sugar solution and dried to a moisture of between 18% and 34% followed by dusting with a moisture binder to prevent sticking. This treatment was designed to maintain the softness of the fruit using the humectant and plasticizing properties of the polyhydric alcohols and sugars. However, some moisture migration still occurs. Also, U.S. Pat. No. 4,542,033 by Agarwala discloses a process for preparing shelf stable fruit pieces wherein fresh fruit pieces are first treated to deactivate enzymatic browning followed by cooking in an acidified sugar syrup then contacting with a sulfiting agent and then dehydrating. The fruit piece prepared in this manner has a soft texture, even when dried to a low water activity (Aw) and can be combined with a ready-to-eat cereal.
Other references of interest include U.S. Pat. No. 3,892,870 by Wood which teaches a process for preparing an artificial fruit comprising making a first matrix of a low-methoxy pectate gel followed by dispersing a starch or agar gel within the pectate gel said starch or agar gel optionally containing fruit pulp. The resulting product is gelled and cut into the desired size. U.S. Pat. No. 4,401,681 by Dahle on the other hand, teaches the prevention of moisture transfer between food products of high and low moisture components by providing an impermeable barrier layer of pectin and dextrose on the exterior of the high moisture component. U.S. Pat. No. 4,504,504 by Gaehring teaches a method of preserving the texture of fresh fruit and vegetable-fruit products wherein diced, pectin-containing fruit pieces are thoroughly impregnated with sodium alginate, then contacted with a calcium solution. A product with a firm texture is obtained. It is believed that the firm texture is a result of the interaction of the gelled matrix of alginate and pectin. U.S. Pat. No. 4,117,112 by Bradshaw discloses a fruit product having a firm outer skin and a softer interior. In the preparation of this product, fruit pulp or puree is mixed with alginate or pectate salt to form a mixture. The mixture is then extruded into drops which are contacted with a calcium solution. The drops upon contact with the calcium solution form a skin of calcium alginate on the outer surface while maintaining a soft core. The drops are subsequently heated to between 70.degree. and 100.degree. C. Finally, U.S. Pat. No. 3,922,360 by Sneath teaches a fruit puree containing calcium which is coated with alginate and extruded into a calcium bath. Notably, the fruit composition itself contains calcium ions which gels the alginate from the inside concomitantly with gelatin by the action of the exterior calcium ions. The skin formed by this process is better defined and more firmly set than a gelation process where calcium is only present in the exterior solution.
It is an object of the present invention to develop a fruit product possessing an Aw of from 0.2 to 0.5 that retains its soft texture in the presence of cereal flakes having a low starting moisture, i.e., cereal having 2-3% moisture.
Another object of the present invention is to provide a fruit piece that remains soft even after the same is combined with a cereal flake and the combination attains equilibration under various storage conditions.
A further object of the present invention is to provide a cereal product which maintains its crispness while packaged with a fruit piece and the combination allowed to equilibrate.